JPH10276324A - Image reading device - Google Patents

Abstract

(57) [Summary] [Problem] To specify the reading start position of a white reference member in the sub-scanning direction, prevent the reading start position from deviating from the white reference member, and lengthen the leading end of the white reference member in the sub-scanning direction. The margins to a minimum. SOLUTION: Among white reference data at both ends A and B in a main scanning direction of a white reference plate 15, white reference data advanced by several lines from a front end line is used as a peak hold block 42a.
The peak is held at 42b, and when it is determined by the determination block 43 that the level is higher than a certain set level, a white reference head line detection signal is output. Then, based on the correction white reference data level, that is, the output of the line sensor 7, the video amplifier (variable amplifier circuit 32)
Set the gain control value of.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus having a one-dimensional line sensor for reading an image in an image scanner, a facsimile, a copying machine or the like. A shading correction technique of reading a reference image, storing the white reference data based on the output of each photoelectric conversion element, and correcting the output of each photoelectric conversion element based on the correction white reference data when reading the image of the document. Regarding improvement.

[0002]

2. Description of the Related Art An image processing unit of an image reading apparatus includes a line sensor (C) having a plurality of one-dimensionally arranged photoelectric conversion elements.
Various types of image processing are performed on image data read using a CD (typified by a CD). One of them is shading correction for correcting sensitivity unevenness and illuminance unevenness for each CCD pixel. In this method, a white reference member for preparing white reference data for correction is prepared outside the effective image reading area of the document reading table (contact glass), and the white reference member is read and stored as white reference data for correction. In actual reading of an original, the output of each CCD is corrected based on the correction white reference data.

Various techniques relating to the shading correction have been proposed. For example, JP-A-3-2898
No. 72 discloses that when reading a white reference for shading correction, a white original is read in a plurality of lines in the sub-scanning direction, and the image data of each read line is divided into a plurality of blocks in the main scanning direction, and the white document is read in the main scanning direction. Each of a plurality of lines of the block corresponding to the same position is sampled, and for the obtained sampling data, a predetermined number of data are removed from the maximum value and the minimum value, and an average value is obtained for the remaining data. Techniques have been proposed for creating shading correction data.

In Japanese Patent Application Laid-Open No. Hei 6-121162, a white reference image in a first area of a white reference member is read by a line sensor, and provisional correction data is stored based on the output of each photoelectric conversion element. A line sensor reads a white reference image in a second region of the white reference member that is displaced in the main scanning direction with respect to one region, and corrects the output of each photoelectric conversion element based on the provisional correction data as provisional corrected data. There has been proposed a technique of storing and specifying a defect of a white reference member based on provisionally corrected data and correcting the provisional correction data based on the specified defect to generate correction data.

[0005]

As described above, a technique for removing noise during white reference reading and performing accurate shading correction has been conventionally known. By the way, the reading of the white reference for performing the shading correction is performed by reading the white reference member before reading the image data, but the movement of the traveling body to the reading position of the white reference member is performed, for example, when a stepping motor is used. In this case, a necessary number of stepping pulses for moving to the position of the white reference member are generated in accordance with the reading position of the white reference member, and the stepping motor is driven by this stepping pulse.

After generating the number of pulses, the video gain control value is read, and the white reference data is read. Here, there is a problem of accuracy in moving to the white reference member position, and a margin is provided in the sub-scanning direction in order to absorb variations in movement accuracy.

However, it is difficult to increase the size of the white reference member without limit, and there is a demand for downsizing of the apparatus itself. Therefore, it is necessary to reliably read the white reference data with the white reference member having a limited size. Must.

If the position of the white reference member for reading the white reference data is deviated from the original position, image data outside the white reference member may be read, and correct shading correction calculation may not be performed. There is a problem that arises.

Therefore, the present invention specifies the reading start position of the white reference member in the sub-scanning direction, prevents the reading start position from deviating from the white reference member, and sets the length of the leading end of the white reference member in the sub-scanning direction. An object of the present invention is to provide an image reading apparatus capable of minimizing a margin.

[0010]

In order to achieve this object, according to the present invention, a white reference image of a white reference member is read by a line sensor having a plurality of one-dimensionally arranged photoelectric conversion elements. A shading correction method of storing the white reference data for correction based on the output of each photoelectric conversion element and correcting the output of each photoelectric conversion element based on the white reference data for correction when reading the image of the document. In an image reading apparatus provided with an image processing device, peak holding means for holding peaks of correction white reference data at both end positions of a white reference member in the main scanning direction. The determination means for determining that the line is a line, and if it is determined that the line is the white reference head line, the video amplifier is determined based on the level of the correction white reference data. Characterized by comprising a gain control value determining means for determining the in-control value.

According to a second aspect of the present invention, when sampling the shading correction data based on the determined gain control value in the first aspect of the invention, newly acquired data is verified.
It is characterized in that it is determined whether or not it should be taken in as correction white reference data.

According to a third aspect of the present invention, in the second aspect of the present invention, when it is determined that the correction white reference data should be taken in, the data is subjected to an averaging process operation of the correction white reference data. In addition to the calculation, when it is determined that the data is not the target, the averaging process of the correction white reference data is performed by replacing the data with the data that has been subjected to the averaging process up to the previous line.

According to a fourth aspect of the present invention, in the second aspect of the invention, when it is determined that the correction white reference data should be taken in, the data is subjected to an averaging processing operation of the correction white reference data. In addition to the calculation, when it is determined that the data is not to be processed, the data to be captured appears and the sampling position of the correction white reference data is changed in the sub-scanning direction until the calculation processing is completed. Sampling of the white reference data is terminated at the time when the calculation processing as the correction white reference data for the pixel is completed.

[0014]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a configuration diagram of the image reading apparatus. An automatic paper feeder (A
DF) 2 is provided, and a document reading table 3 is provided on the upper surface of the main body, thereby constituting an image scanner. In this case, the light source 4 a
A first traveling body 4 having a mirror 4b and a mirror 5b
a second traveling body 5 having a and 5b, a lens 6, a one-dimensional photoelectric conversion element (a CCD is used in this example) 7,
An exposure scanning optical system 9 including a stepping motor 8 for driving the first and second traveling bodies 4 and 5 is provided. The description of the lower configuration of the exposure scanning optical system 9 is omitted here.

The automatic paper feeder 2 has an ADF unit 10 and a document table 11. A stepping motor 12 is provided in the ADF unit 10. Further, a document holding plate 1 is provided on the document reading table 3.
A document 13 is set below the document pressing plate 14. Document reading table 3
A white reference plate 15 for shading correction is disposed at the end of the white reference plate 15.

FIG. 2 is an overall control block diagram of the image reading apparatus. FIG. 3 is a configuration diagram of the document reading unit in the book mode, and FIG. 4 is a configuration diagram of the document reading unit in the ADF mode. The image reading apparatus shown in FIG.
CD 7, stepping motors 8, 12, CPU 16, light source driver 17, CCD driving unit 18, image processing unit 19,
Motor drivers 20, 28, scan buffer 25, I
/ F controller 26 and a buffer controller 27.

As a document reading mode, a book mode in which image data is read using a document reading table 3 as shown in FIG. 3 and a reading mode of image data using an automatic paper feeder 2 as shown in FIG. And ADF mode.

First, the basic operation of reading image data in the book mode as shown in FIG. 3 will be described. After setting the document 13 on the document reading table 3 below the document pressing plate 14, the CPU 16 operates the light source driver 17 to turn on the light source 4a. Next, the white reference plate 15 is read by the CCD 7 driven by the CCD driving unit 18, and an A / D converter (not shown) in the image processing unit 19.
Performs analog-to-digital conversion, and stores the reference data for shading correction of image data in a RAM (not shown) in the image processing unit 19.

The CPU 16 drives a motor driver (driving device) 20 to operate the stepping motor 8, whereby the first traveling body 4 moves in a certain direction of the document 13. When the first traveling body 4 scans the document surface at a constant speed, the image data of the document 13 is transferred to the CCD 7.
Is subjected to photoelectric conversion.

FIG. 5 is a block diagram showing the most basic configuration of the image processing section 19 shown in FIG. The image processing unit 19 illustrated in FIG. 5 includes an analog video processing unit 21, a shading correction processing unit 22, an image data processing unit 23, and a binarization processing unit 24. Here, the analog video signal a photoelectrically converted is subjected to digital conversion processing in an analog video processing unit 21 and then to a shading correction processing unit 2.
2. After performing shading correction and various types of image data processing by the image data processing unit 23, the binarization processing unit 24 creates the desired binarized data b by the binarization processing unit 24. Thereafter, the binarized data b is sequentially stored in the scan buffer 25.

The I / F controller 26 controls output of data in the scan buffer 25 to an external device such as a host computer (not shown). The buffer controller 27 manages input / output of image data to / from the scan buffer 25.

Next, the basic operation of reading image data in the ADF mode as shown in FIG. 4 will be described. Also in this case, first, after the white reference plate 15 is read, the CPU 16 drives the stepping motor 12 by the motor driver (driving device) 28 so that the original table 1 is read.
The document 13 set to 1 is transported by the separation roller 29 and the transport roller 30, and is transported to a predetermined reading position of the first traveling body 4. At this time, the document 13 is conveyed at a constant speed, and the CCD 7 reads the image data of the document surface while the first traveling body 4 is stopped.

Hereinafter, the same processing as in the book mode is performed.
The binarized image data is stored in the scan buffer 25 and sent to a host computer (not shown) or the like via the I / F controller 26.

FIG. 6 is a block diagram showing the image processing section 19 shown in FIG. 5 in further detail. The analog video processing section 21 shown in FIG. 5 includes a preamplifier circuit 31 and a variable amplifier circuit 32. The shading correction processing unit 2
2 includes an A / D converter 33, a black operation circuit 34, a shading correction operation circuit 35, and a line buffer 36.

The original 13 on the original reading table 3 is irradiated by the light source 4a, and the reflected light is reflected by the shading adjusting plate 37.
The light is condensed by a lens 6 through the light source, and is imaged by a line sensor 7. In FIG. 6, a mirror for folding the reflected light is omitted for simplification of the description. The shading adjustment plate 37 plays a role of adjusting the amount of light for eliminating the difference in the amount of reflected light between the center and the end of the line sensor 7.
This is because if there is too much difference in the amount of reflected light between the central part and the end part of the line sensor in the shading calculation processing, only a calculation result containing a large amount of distortion can be obtained.
This is for performing shading arithmetic processing after eliminating the difference in the amount of reflected light in advance.

FIGS. 7A and 7B are explanatory diagrams showing the difference in reproduction level depending on the presence or absence of a shading adjustment plate.
FIG. 7A shows a reproduction level distribution when the video data of the white reference plate 15 is read without the adjustment plate 37.
Thus, the level at the center is high and the level drops at the ends. FIG. 7B is an example of a level distribution when the shading adjustment plate 37 is used. After the photoelectric conversion by the line sensor 7, the level is adjusted as analog video data,
Digital conversion is performed by the A / D converter 33. In the digitized video data, a portion corresponding to an offset on the black side is removed by the arithmetic processing of the black arithmetic circuit 34 and sent to the shading correction arithmetic circuit 35.

Although not described in detail, the offset on the black side at this time includes a difference between channels when the output from the line sensor 7 has a two-channel configuration. The arithmetic processing here has a great purpose particularly to remove error components between channels.

Before performing the sampling processing of the white reference data, data for gain setting must be read in order to determine the gain value of the amplification processing for the video data. The white reference plate 15 is read at a set fixed gain value, and peak detection processing of pixels in the read line data is performed. The peak value is used as a gain setting for amplification processing on video data. Therefore, the image data is read from the sampling of the white reference data for the shading calculation processing with the gain value.

The peak data for gain setting is detected by detecting the first line of the white reference plate 15 in the sub-scanning direction. The head position of the white reference plate 15 needs to be a black member. The black member can be separated from the white reference plate 15. An example of processing for detecting the leading line of the white reference plate 15 is shown.

FIG. 8 shows detection positions A and B in the video level data of the white reference plate. FIG. 9 is a block diagram of a white reference plate leading line detection circuit, and FIG. 10 is a timing diagram of a white reference plate leading line detection and peak hold data sampling line. The detection block 41 shown in FIG. 9 for outputting a white reference head line detection signal based on the image data in the range A and the range B shown in FIG. 8 includes a peak hold block 41a for the range A image data and a peak hold block 41a for the range B image data. And a white reference head line determination block 43 for determining a white reference head line based on these outputs.
It has.

If the outside of the white reference plate 15 is black, the video data has almost no level. The detection position in this level data is the range of A and B. A peak hold process is performed within the range of A and B, and when the detected level is higher than a certain set level, the determination block 43 determines that the data is obtained by reading the white reference plate 15, and converts the line data to white. It is determined that the position is the head line position of the reference plate 15.

The reason why the peak hold processing is performed at both ends of the white reference plate 15 in the main scanning direction of A and B is that if the white reference plate 15 is installed obliquely depending on the mounting state of the white reference plate 15, , B are determined to be white reference head lines only after they are determined to be the white reference plate 15. Therefore, both ends are set as the detection positions.

If it is determined that only one side is the white reference plate 15, the white reference plate 15 is installed obliquely, and the white reference plate 15 cannot be read correctly.
In addition, since there is a possibility that the state of reflection at the edge portion of the white reference plate 15 may change significantly, the peak hold process may be performed by reading the white reference plate 15 a few lines after detecting the leading end line. desirable. By performing this processing, the front end line of the white reference plate 15 is detected, and the peak hold processing is performed based on the detection of the front end line, whereby the correct gain setting for the video amplifier can be performed.

A correct gain setting is made for the video data amplification processing, and white reference data is sampled by the gain setting. At the time of the sampling process, it is determined whether the white reference data sampled in the main scanning direction and the sub-scanning direction may be newly added to the average calculation process of the white reference data.

In this case, for example, the level difference between adjacent pixels in the main scanning direction is set to be within the range. If a level difference exceeding the difference setting is detected, it is determined that the pixel is an abnormal pixel. I do. Similarly, in the sub-scanning direction, how many levels are different from the previous line data is set in advance, and if a difference greater than the level difference is detected, it is determined that the pixel is an abnormal pixel. In this example, both the main scanning direction and the sub-scanning direction are detected as abnormal pixels. However, the same applies to a single process in the main scanning direction and the sub-scanning direction.

When it is determined that the newly fetched data should be fetched as white reference data, the data is added to the calculation processing as an object of averaging processing of the white reference data by the average value processing calculation block. Conversely, when it is determined that the data is out of the target, the data subjected to the averaging process up to the previous line is replaced with the current data, and the averaging process of the white reference data is performed. By performing this processing, white reference data that does not include abnormal pixels can be formed.

FIG. 11 is a block diagram showing a first example of the white reference data loading determination processing and the averaging calculation processing.
Line buffer 51 for storing white reference data, sub-scanning direction difference detection block 52, main scanning direction difference detection block 5
3. An averaging processing operation block 54 is provided.

The comparison between the new read data and the averaging processing data up to the previous line is performed by the sub-scanning direction difference detection block 52, and the main scanning direction difference detection block 53 is used for the main scanning direction. With respect to the main scanning direction, comparison processing is performed with the pixel in the main scanning direction one timing before, and it is determined whether the new read data is to be added to the averaging processing operation by the averaging processing operation block 54 based on the difference result. In addition,
The difference amount is given in the form of a set threshold.

The averaging operation processing block 54 receives the result of the determination, and performs a process as to whether the newly read data is included in the operation processing or the averaging processing data up to the previous line is used for the operation, and generates white reference data. . For example, when the averaging process is performed on four data, four lines of data are read to generate white reference data.

When it is determined that the newly acquired data should be acquired as white reference data, the data is added to the arithmetic processing as an object of the averaging processing operation of the white reference data. On the other hand, if it is determined that the data is out of the target, the arithmetic processing is not performed. The sampling of the data is continued, and the sampling of the white reference data is completed when the arithmetic processing as the white reference data of each pixel is completed.
By performing this processing, it is possible to form white reference data that does not include an abnormal pixel and that has new data subjected to arithmetic processing for the averaging processing.

FIG. 12 is a block diagram showing a second example of the white reference data loading determination processing and the averaging calculation processing.
In addition to the sub-scanning direction difference detection block 52 and the main scanning direction difference detection block 53, a line buffer 61 for storing white reference data and storing a pixel count value for calculation processing, and a block 62 for averaging processing and calculation processing count processing are provided. Prepare.

The difference detection in the main scanning direction and the sub-scanning direction is as described above. However, when averaging, for example, when averaging four data, the newly read data is applied to the averaging operation. In a block 62, whether or not it is added is counted for each pixel unit, and the count result is stored in the line buffer 61 together with the white reference data. This count value is 4 in all the white reference data.
, The sampling of the white reference data ends.

[0043]

According to the first aspect of the present invention, by specifying the reading start position of the white reference member in the sub-scanning direction,
It is possible to prevent the reading start position from deviating from the white reference member, and to minimize the length margin of the sub-scanning leading end of the white reference member.

According to the second aspect of the present invention, it is possible to prevent defective pixels from being included in the arithmetic processing as white reference data.

According to the third aspect of the present invention, since re-reading by detecting a defective pixel is not performed, it is possible to eliminate processing overhead.

According to the fourth aspect of the present invention, it is possible to generate highly accurate white reference data that does not include a defective pixel in the white reference data.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an image reading apparatus.

FIG. 2 is an overall control block diagram of the image reading apparatus.

FIG. 3 is a configuration diagram of a document reading unit in a book mode.

FIG. 4 is a configuration diagram of a document reading unit in an ADF mode.

FIG. 5 is a block diagram illustrating the most basic configuration of the image processing unit illustrated in FIG. 2;

FIG. 6 is a block diagram showing the image processing unit shown in FIG. 5 in further detail;

FIG. 7 is an explanatory diagram showing a difference in reproduction level depending on the presence or absence of a shading adjustment plate.

FIG. 8 shows a detection position A in video level data of a white reference plate.
FIG.

FIG. 9 is a block diagram of a white reference plate leading line detection circuit.

FIG. 10 is a timing chart of a white reference plate leading line detection and peak hold data sampling line.

FIG. 11 is a block diagram illustrating a first example of a white reference data capturing determination process and an averaging calculation process.

FIG. 12 is a block diagram illustrating a second example of the white reference data capturing determination process and the averaging calculation process.

[Explanation of symbols]

 15 White reference plate 19 Image processing unit 21 Analog video processing unit 22 Shading correction processing unit 23 Image data processing unit 24 Binarization processing unit 35 Shading correction operation circuit 41 White reference plate head line detection block 42a, 42b Peak hold block 43 White Reference first line judgment block

Claims (4)

[Claims] 1. A white sensor which reads a white reference image of a white reference member by a line sensor having a plurality of one-dimensionally arranged photoelectric conversion elements, stores the white reference image as correction white reference data based on the output of each photoelectric conversion element, and When reading the image of
In an image reading apparatus provided with an image processing device adopting a shading correction method for correcting the output of each photoelectric conversion element based on the correction white reference data, the correction white reference data is set at both ends of the white reference member in the main scanning direction. A peak hold means for performing peak hold of, a determination means for determining, when the peak hold value is equal to or higher than a predetermined level, a white reference head line, and a correction white reference data when determined to be a white reference head line. An image reading device comprising a gain control value determining means for determining a gain control value of the video amplifier based on the level of the video amplifier. 2. The image reading apparatus according to claim 1, wherein when sampling the shading correction data based on the determined gain control value, the newly read data is verified to obtain correction white reference data. An image reading apparatus for determining whether or not the image should be taken in as an image. 3. The image reading apparatus according to claim 2, wherein when it is determined that the correction white reference data is to be taken in, the data is added to the calculation as an object of averaging processing of the correction white reference data. An image reading apparatus, wherein when it is determined that the data is outside the range, the averaging process is performed on the correction white reference data by replacing the data with the data that has been subjected to the averaging process up to the previous line. 4. The image reading apparatus according to claim 2, wherein when it is determined that the correction white reference data should be taken in, the data is added to the calculation as an object of averaging processing of the correction white reference data. If it is determined that the pixel is to be taken outside, sampling of the correction white reference data is continued by changing the sampling position of the correction white reference data in the sub-scanning direction until the calculation processing is completed and the correction white reference data of each pixel is continued. An image reading apparatus, wherein sampling of white reference data is completed at the time of completion of calculation processing as reference data.